In general, a fuel cell converts chemical energy into electrical energy through a redox reaction of hydrogen and oxygen. A unit cell of the fuel cell has a low output voltage. Thus, several to hundreds of unit cells are generally stacked into a fuel cell stack. A separator provides an electrical connection between the unit cells during stacking the unit cells and acts as flow fields by which reactant gases are separated and through which coolant flows.
For a typical separator, the volume and weight of the fuel cell stack can be reduced by reducing the thickness during a manufacturing process, such as stamping, etc., which allows for mass production.
A metal separator has advantages, such as high electrical conductivity and excellent mechanical properties and processability. However, the typical metal separator can be easily corroded in a hot and humid environment of the fuel cell.
Conventionally, a technique of coating a polymer composite material comprising a conductive additive on the surface of the separator has been developed to solve the problem.
The separator for a polymer electrolyte fuel cell provides a passage through which coolant passes to remove heat generated during the operation.
As shown in FIG. 8, the conventional separator comprises two sheets of metal plates 1 and 2, as base materials for the passage through which coolant passes. Contact resistance is generated on a surface between the two metal plates.
A polymer composite material coated on the two metal plates creates a contact surface between a composite material coating layer 3 and a composite material coating layer 4 as well as between each composite material coating layer and the metal plate generating high contact resistance, thus reducing the efficiency of the fuel cell.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.